Do not pin SID to a specific IP address

[DL6ER]

What does this implement/fix?

A very simple change, see the title. This PR is the result of the discussion in #1779.

We furthermore fix a small wording issue and extend the description of the POST /auth API endpoint:

edit Updated screenshot

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Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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